Roofing membranes, compositions, and methods of making the same

ABSTRACT

A roofing membrane and a method of making the same is provided. The roofing membrane includes a top layer having a flame retardant and a first silane-crosslinked polyolefin elastomer with a density less than 0.90 g/cm 3 ; a scrim layer; and a bottom layer having a flame retardant and a second silane-crosslinked polyolefin elastomer with a density less than 0.90 g/cm 3 . The top and bottom layers of the roofing membrane both exhibit a compression set of from about 5.0% to about 35.0%, as measured according to ASTM D 395 (22 hrs @ 70° C.).

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. 119(e) to U.S.Provisional Patent Application No. 62/497,959, filed Dec. 10, 2016,entitled “HOSE, COMPOSITION INCLUDING SILANE-GRAFTED POLYOLEFIN, ANDPROCESS OF MAKING A HOSE,” and to U.S. Provisional Patent ApplicationNo. 62/497,954 filed Dec. 10, 2016, entitled “WEATHERSTRIP, COMPOSITIONINCLUDING SILANE-GRAFTED POLYOLEFIN, AND PROCESS OF MAKING AWEATHERSTRIP,” both of which are herein incorporated by reference intheir entirety.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to compositions that may beused to form thermoplastic roofing membranes, and more particularly, tosilane-grafted polyolefin elastomer compositions used to formthermoplastic roofing membranes and methods for manufacturing thesecompositions and roofing membranes.

BACKGROUND OF THE DISCLOSURE

Thermoplastic roofing membranes may be a single layer or may be composedof multiple layers and may contain a reinforcing fabric or scrimreinforcement material in the center between any two of the layers ofthe roofing membrane. Each of the respective layers in the roofingmembrane needs to demonstrate a variety of different material propertiesin order to be suited for use on a roof where the material will beexposed to the sun and the elements. The material properties of thepolymer layers should exhibit good adhesion, UV resistance,weatherability (durability), flame retardance, flexibility, chemicalresistance and longevity. In addition, roofing membranes shouldpreferably be capable of forming hot-air welded seams.

Many different polymer systems are available to be used for roofingmembranes. The most commonly used polymer systems include thermoplasticpolyolefin (TPO), ethylene propylene diene monomer (EPDM), and polyvinylchloride (PVC). Depending on the material(s) selected, differentadvantages and disadvantages are typically observed. TPO membranes arewidely available, affordable, and typically white, but are susceptibleto deterioration when exposed to high heat and/or solar UV radiation.EPDM membranes are made from the readily available EPDM syntheticrubber, but roughly 95% of all EPDM roofing membranes produced are blackwhile federal and state building regulators are starting to push forwhite roofing membranes. Lastly, PVC membranes are widely available andoffer excellent puncture, heat-weldability, colorability, and heatresistant qualities, but these membranes can be expensive to manufactureand suffer from variability in properties as produced by differentmanufacturers.

Mindful of the advantages and drawbacks for the various TPO, EPDM, andPVC materials used to make roofing membranes, manufacturers have a needfor the development of new polymer compositions and methods of makingroofing membranes that are simpler with less production variability,lighter in weight and color, and have superior durability over a longerperiod of time.

SUMMARY OF THE DISCLOSURE

According to one aspect of the present disclosure, a roofing membrane isdisclosed. The single ply roofing membrane includes a top layercomprising a flame retardant and first silane-crosslinked polyolefinelastomer having a density less than 0.90 g/cm³; a scrim layer; and abottom layer comprising a flame retardant and a secondsilane-crosslinked polyolefin elastomer having a density less than 0.90g/cm³. The top and bottom layers of the roofing membrane both exhibit acompression set of from about 5.0% to about 35.0%, as measured accordingto ASTM D 395 (22 hrs @ 70° C.).

According to another aspect of the present disclosure, a method ofmaking a roofing membrane is provided. The method includes: extruding afirst silane-crosslinkable polyolefin elastomer to form a top layer;extruding a second silane-crosslinkable polyolefin elastomer to form abottom layer; calendaring a scrim layer between the top and the bottomlayers to form an uncured roofing membrane element; and crosslinking thesilane-crosslinkable polyolefin elastomers of the top and the bottomlayers in the uncured roofing membrane element at a curing temperatureand a curing humidity to form the roofing membrane. The top and bottomlayers of the roofing membrane both exhibit a compression set of fromabout 5.0% to about 35.0%, as measured according to ASTM D 395 (22 hrs @70° C.).

According to a further aspect of the present disclosure, a method ofmaking a high-load flame retardant thermoplastic polyolefin (TPO)roofing membrane is provided. The method includes: adding asilane-grafted polyolefin elastomer, a fire retardant, and acondensation catalyst to a reactive single screw extruder to produce asilane-crosslinkable polyolefin elastomer; calendaring thesilane-crosslinkable polyolefin elastomer to form a top layer and abottom layer; calendaring a scrim layer between the top and the bottomlayers to form an uncured roofing membrane element; and crosslinking thesilane-crosslinkable polyolefin elastomers of the top and the bottomlayers in the uncured roofing membrane element at an ambient temperatureand an ambient humidity to form the thermoplastic polyolefin (TPO)roofing membrane. The top and bottom layers of the thermoplasticpolyolefin (TPO) roofing membrane both exhibit a compression set of fromabout 5.0% to about 35.0%, as measured according to ASTM D 395 (22 hrs @70° C.).

These and other aspects, objects, and features of the present disclosurewill be understood and appreciated by those skilled in the art uponstudying the following specification, claims, and appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a cross-sectional view of a roofing membrane according to someaspects of the present disclosure;

FIG. 2 is a schematic reaction pathway used to produce asilane-crosslinked polyolefin elastomer according to some aspects of thepresent disclosure;

FIG. 3 is a flow diagram of a method for making a single ply roofingmembrane with a silane-crosslinked polyolefin elastomer using a two-stepSioplas approach according to some aspects of the present disclosure;

FIG. 4A is a schematic cross-sectional view of a reactive twin-screwextruder according to some aspects of the present disclosure;

FIG. 4B is a schematic cross-sectional view of a single-screw extruderaccording to some aspects of the present disclosure;

FIG. 5 is a flow diagram of a method for making a single ply roofingmembrane with a silane-crosslinked polyolefin elastomer using a one-stepMonosil approach according to some aspects of the present disclosure;

FIG. 6 is a schematic cross-sectional view of a reactive single-screwextruder according to some aspects of the present disclosure;

FIG. 7 is a graph illustrating the stress/strain behavior of asilane-crosslinked polyolefin elastomer, according to aspects of thedisclosure, as compared to conventional EPDM compounds;

FIG. 8 is a relaxation plot of an exemplary silane-crosslinkedpolyolefin elastomer, suitable for a roofing membrane according toaspects of the disclosure, and comparative EPDM cross-linked materials;and

FIG. 9 is a compression set plot of an exemplary silane-crosslinkedpolyolefin elastomer suitable for a roofing membrane, and a comparativeEPDM cross-linked material.

DETAILED DESCRIPTION OF THE EMBODIMENTS

For purposes of description herein the terms “upper,” “lower,” “right,”“left,” “rear,” “front,” “vertical,” “horizontal,” and derivativesthereof shall relate to the roofing membranes of the disclosure as shownin FIG. 1. However, it is to be understood that the device may assumevarious alternative orientations and step sequences, except whereexpressly specified to the contrary. It is also to be understood thatthe specific devices and processes illustrated in the attached drawings,and described in the following specification are simply exemplaryembodiments of the inventive concepts defined in the appended claims.Hence, specific dimensions and other physical characteristics relatingto the embodiments disclosed herein are not to be considered aslimiting, unless the claims expressly state otherwise.

All ranges disclosed herein are inclusive of the recited endpoint andindependently combinable (for example, the range of “from 2 to 10” isinclusive of the endpoints, 2 and 10, and all the intermediate values).The endpoints of the ranges and any values disclosed herein are notlimited to the precise range or value; they are sufficiently impreciseto include values approximating these ranges and/or values.

A value modified by a term or terms, such as “about” and“substantially,” may not be limited to the precise value specified. Theapproximating language may correspond to the precision of an instrumentfor measuring the value. The modifier “about” should also be consideredas disclosing the range defined by the absolute values of the twoendpoints. For example, the expression “from about 2 to about 4” alsodiscloses the range “from 2 to 4.”

As used herein, the term “and/or,” when used in a list of two or moreitems, means that any one of the listed items can be employed by itself,or any combination of two or more of the listed items can be employed.For example, if a composition is described as containing components A,B, and/or C, the composition can contain A alone; B alone; C alone; Aand B in combination; A and C in combination; B and C in combination; orA, B, and C in combination.

Referring to FIG. 1, a roofing membrane 10 is disclosed. The roofingmembrane 10 includes a top layer 14 having a flame retardant and a firstsilane-crosslinked polyolefin elastomer with a density less than 0.90g/cm³; a scrim layer 26; and a bottom layer 38 having a flame retardantand a second silane-crosslinked polyolefin elastomer with a density lessthan 0.90 g/cm³. The top and bottom layers of the roofing membrane bothexhibit a compression set of from about 5.0% to about 35.0%, as measuredaccording to ASTM D 395 (22 hrs @ 70° C.).

A TPO roofing membrane must exhibit at least the following mechanicalproperties as outlined by the ASTM specification for TPO roofingmembranes: 1) a tensile strength (CD and MD) greater than 10 MPa; 2) anelongation at break (CD and MD) greater than 500%; 3) an elastic modulus(CD and MD) of less than 100 MPa; and 4) a flame retardance rating ofclassification D as measured in accordance with the EN ISO 11925-2surface exposure test.

Referring again to FIG. 1, a cross-sectional view of the single plyroofing membrane 10 is provided. The single ply roofing membrane 10includes the top layer 14 with a first and a second surface 18, 22. Thescrim layer 26 (also referred to as scrim 26) has a third and a fourthsurface 30, 34 where the third surface 30 of the scrim 26 is coupled tothe second surface 22 of the top layer 14. The single ply roofingmembrane 10 additionally includes a bottom layer 38 with a fifth and asixth surface 42, 46, where the fifth surface 42 of the bottom layer 38is coupled to the fourth surface 34 of the scrim 26. In some aspects,the roofing membrane 10 may include the single ply roofing membrane, adouble ply roofing membrane, or a higher number of plies. Unlessotherwise denoted, roofing membrane 10 and single ply roofing membrane10 both mean a single ply made from the top layer 14, scrim layer 26,and bottom layer 38.

The scrim layer 26 disposed between the top and bottom layers 14, 38 canserve as a reinforcement in the roofing membrane, thus adding to itsstructural integrity. Materials that can be used for the scrim layers 26may include, for example, woven and/or non-woven fabrics, fiberglass,and/or polyester. In some aspects, additional materials that can be usedfor the scrim layers 26 can include synthetic materials such aspolyaramids, KEVLAR™, TWARON™, polyamides, polyesters, RAYON™, NOMEX™,TECHNORA™, or a combination thereof. In some aspects, the scrim layer 26may include aramids, polyamides, and/or polyesters. In some aspects, atenacity of the scrim layer 26 may range from about 100 to about 3000denier. In other aspects, the scrim layers 26 may have a tenacityranging from about 500 to about 1500 denier. In still other aspects,scrim layers 26 may have a tenacity of about 1000 denier. In someaspects, scrim layers 26 may have a tensile strength of greater thanabout 14 kN per meter (80 pounds force per inch). In other aspects, thescrim layers 26 may have a tensile strength of greater than about 10 kNper meter, greater than about 15 kN per meter, greater than about 20 kNper meter, or greater than about 25 kN per meter. Depending on thedesired properties of the final single ply roofing membrane 10, thescrim layers 26 may be varied as needed to suit particular roofingmembrane designs. One of ordinary skill in the art would appreciate thatsuch characteristics can be varied without departing from the presentdisclosure.

The single ply roofing membranes 10 disclosed herein may have a varietyof different dimensions. In some aspects, single ply roofing membranes10 may have a length from about 30 feet to about 200 feet and a widthfrom about 4 feet to about 12 feet. In some aspects, the roofingmembranes 10 may have a width of about 10 feet. Variations in the widthmay provide for various advantages. For example, in some aspects,roofing membranes 10 having smaller widths may advantageously allow forgreater ease in assembly of a roofing structure. Smaller widths may alsoadvantageously allow for greater ease in rolling or packaging of amanufactured membrane. Larger widths may advantageously allow forgreater structure integrity, fast installation and/or improve thestability of a roofing structure comprising these membranes.

Numerous different flame retardants may be used in combination with thefirst and second silane-crosslinkable polyolefin elastomer employed inthe top and bottom layers 14, 38 of the roofing membrane 10. Forexample, magnesium hydroxide may provide flame retardant properties inthe layers 14, 38. Magnesium hydroxide may be extruded or blended withthe silane-grafted polyolefin elastomer to ensure complete dispersal inthe composition blend. In some aspects, the magnesium hydroxide isblended with the silane-grafted polyolefin elastomer in an amount up to70 wt % magnesium hydroxide. In another exemplary embodiment, themagnesium hydroxide in the silane-grafted polyolefin elastomer can makeup between about 20 wt % and 75 wt % of the roofing membranecomposition.

The disclosure focuses on the composition, method of making thecomposition, methods of making roofing membranes with thesecompositions, and the corresponding material properties for thesilane-crosslinked polyolefin elastomer used to make single ply roofingmembranes 10 (as depicted in FIG. 1), along with other roofing membranes10 consistent with the principles of this disclosure. The roofingmembrane 10 is formed from a silane-grafted polyolefin where thesilane-grafted polyolefin may have a catalyst added to form asilane-crosslinkable polyolefin elastomer. This silane-crosslinkablepolyolefin may then be crosslinked upon exposure to moisture and/or heatto form the final silane-crosslinked polyolefin elastomer or blend. Inaspects, the silane-crosslinked polyolefin elastomer or blend includesthe first polyolefin having a density less than 0.90 g/cm³, the secondpolyolefin having a crystallinity of less than 40%, the silanecrosslinker, the graft initiator, and the condensation catalyst.

First Polyolefin

The first polyolefin can be a polyolefin elastomer including an olefinblock copolymer, an ethylene/α-olefin copolymer, a propylene/α-olefincopolymer, EPDM, EPM, or a mixture of two or more of any of thesematerials. Exemplary block copolymers include those sold under the tradenames INFUSE™, an olefin block co-polymer (the Dow Chemical Company) andSEPTON™ V-SERIES, a styrene-ethylene-butylene-styrene block copolymer(Kuraray Co., LTD.). Exemplary ethylene/α-olefin copolymers includethose sold under the trade names TAFMER™ (e.g., TAFMER DF710) (MitsuiChemicals, Inc.), and ENGAGE™ (e.g., ENGAGE 8150) (the Dow ChemicalCompany). Exemplary propylene/α-olefin copolymers include those soldunder the trade name VISTAMAXX™ 6102 grades (Exxon Mobil ChemicalCompany), TAFMER™ XM (Mitsui Chemical Company), and VERSIFY™ (DowChemical Company). The EPDM may have a diene content of from about 0.5to about 10 wt %. The EPM may have an ethylene content of 45 wt % to 75wt %.

The term “comonomer” refers to olefin comonomers which are suitable forbeing polymerized with olefin monomers, such as ethylene or propylenemonomers. Comonomers may comprise but are not limited to aliphaticC₂-C₂₀ α-olefins. Examples of suitable aliphatic C₂-C₂₀ α-olefinsinclude ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene,1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene,1-octadecene and 1-eicosene. In an embodiment, the comonomer is vinylacetate. The term “copolymer” refers to a polymer, which is made bylinking more than one type of monomer in the same polymer chain. Theterm “homopolymer” refers to a polymer which is made by linking olefinmonomers, in the absence of comonomers. The amount of comonomer can, insome embodiments, be from greater than 0 wt %to about 12 wt % based onthe weight of the polyolefin, including from greater than 0 wt % toabout 9 wt %, and from greater than 0 wt % to about 7 wt %. In someembodiments, the comonomer content is greater than about 2 mol % of thefinal polymer, including greater than about 3 mol % and greater thanabout 6 mol %. The comonomer content may be less than or equal to about30 mol %. A copolymer can be a random or block (heterophasic) copolymer.In some embodiments, the polyolefin is a random copolymer of propyleneand ethylene.

In some aspects, the first polyolefin is selected from the groupconsisting of: an olefin homopolymer, a blend of homopolymers, acopolymer made using two or more olefins, a blend of copolymers eachmade using two or more olefins, and a combination of olefin homopolymersblended with copolymers made using two or more olefins. The olefin maybe selected from ethylene, propylene, 1-butene, 1-propene, 1-hexene,1-octene, and other higher 1-olefin. The first polyolefin may besynthesized using many different processes (e.g., using gas phase andsolution based metallocene catalysis and Ziegler-Natta catalysis) andoptionally using a catalyst suitable for polymerizing ethylene and/orα-olefins. In some aspects, a metallocene catalyst may be used toproduce low density ethylene/α-olefin polymers.

In some aspects, the polyethylene used for the first polyolefin can beclassified into several types including, but not limited to, LDPE (LowDensity Polyethylene), LLDPE (Linear Low Density Polyethylene), and HDPE(High Density Polyethylene). In other aspects, the polyethylene can beclassified as Ultra High Molecular Weight (UHMW), High Molecular Weight(HMW), Medium Molecular Weight (MMW) and Low Molecular Weight (LMW). Instill other aspects, the polyethylene may be an ultra-low densityethylene elastomer.

In some aspects, the first polyolefin may include a LDPE/silanecopolymer or blend. In other aspects, the first polyolefin may bepolyethylene that can be produced using any catalyst known in the artincluding, but not limited to, chromium catalysts, Ziegler-Nattacatalysts, metallocene catalysts or post-metallocene catalysts.

In some aspects, the first polyolefin may have a molecular weightdistribution M_(w)/M_(n) of less than or equal to about 5, less than orequal to about 4, from about 1 to about 3.5, or from about 1 to about 3.

The first polyolefin may be present in an amount of from greater than 0to about 100 wt % of the composition. In some embodiments, the amount ofpolyolefin elastomer is from about 30 wt % to about 70 wt %. In someaspects, the first polyolefin fed to an extruder can include from about50 wt % to about 80 wt % of an ethylene/α-olefin copolymer, includingfrom about 60 wt % to about 75 wt %, and from about 62 wt % to about 72wt %.

The first polyolefin may have a melt viscosity in the range of fromabout 2,000 cP to about 50,000 cP as measured using a Brookfieldviscometer at a temperature of about 177° C. In some embodiments, themelt viscosity is from about 4,000 cP to about 40,000 cP, including fromabout 5,000 cP to about 30,000 cP and from about 6,000 cP to about18,000 cP.

The first polyolefin may have a melt index (T2), measured at 190° C.under a 2.16 kg load, of from about 20.0 g/10 min to about 3,500 g/10min, including from about 250 g/10 min to about 1,900 g/10 min and fromabout 300 g/10 min to about 1,500 g/10 min. In some aspects, the firstpolyolefin has a fractional melt index of from 0.5 g/10 min to about3,500 g/10 min.

In some aspects, the density of the first polyolefin is less than 0.90g/cm³, less than about 0.89 g/cm³, less than about 0.88 g/cm³, less thanabout 0.87 g/cm³, less than about 0.86 g/cm³, less than about 0.85g/cm³, less than about 0.84 g/cm³, less than about 0.83 g/cm³, less thanabout 0.82 g/cm³, less than about 0.81 g/cm³, or less than about 0.80g/cm³. In other aspects, the density of the first polyolefin may be fromabout 0.85 g/cm³ to about 0.89 g/cm³, from about 0.85 g/cm³ to about0.88 g/cm³, from about 0.84 g/cm³ to about 0.88 g/cm³, or from about0.83 g/cm³ to about 0.87 g/cm³. In still other aspects, the density isat about 0.84 g/cm³, about 0.85 g/cm³, about 0.86 g/cm³, about 0.87g/cm³, about 0.88 g/cm³, or about 0.89 g/cm³.

The percent crystallinity of the first polyolefin may be less than about60%, less than about 50%, less than about 40%, less than about 35%, lessthan about 30%, less than about 25%, or less than about 20%. The percentcrystallinity may be at least about 10%. In some aspects, thecrystallinity is in the range of from about 2% to about 60%.

Second Polyolefin

The second polyolefin can be a polyolefin elastomer including an olefinblock copolymer, an ethylene/α-olefin copolymer, a propylene/α-olefincopolymer, EPDM, EPM, or a mixture of two or more of any of thesematerials. Exemplary block copolymers include those sold under the tradenames INFUSE™ (the Dow Chemical Company) and SEPTON™ V-SERIES (KurarayCo., LTD.). Exemplary ethylene/α-olefin copolymers include those soldunder the trade names TAFMER™ (e.g., TAFMER DF710) (Mitsui Chemicals,Inc.) and ENGAGE™ (e.g., ENGAGE 8150) (the Dow Chemical Company).Exemplary propylene/α-olefin copolymers include those sold under thetrade name TAFMER™ XM grades (Mitsui Chemical Company) and VISTAMAXX™(e.g., VISTAMAXX 6102) (Exxon Mobil Chemical Company). The EPDM may havea diene content of from about 0.5 to about 10 wt %. The EPM may have anethylene content of 45 wt % to 75 wt %.

In some aspects, the second polyolefin is selected from the groupconsisting of: an olefin homopolymer, a blend of homopolymers, acopolymer made using two or more olefins, a blend of copolymers eachmade using two or more olefins, and a blend of olefin homopolymers withcopolymers made using two or more olefins. The olefin may be selectedfrom ethylene, propylene, 1-butene, 1-propene, 1-hexene, 1-octene, andother higher 1-olefin. The first polyolefin may be synthesized usingmany different processes (e.g., using gas phase and solution basedmetallocene catalysis and Ziegler-Natta catalysis) and optionally usinga catalyst suitable for polymerizing ethylene and/or α-olefins. In someaspects, a metallocene catalyst may be used to produce low densityethylene/α-olefin polymers.

In some aspects, the second polyolefin may include a polypropylenehomopolymer, a polypropylene copolymer, a polyethylene-co-propylenecopolymer, or a mixture thereof. Suitable polypropylenes include but arenot limited to polypropylene obtained by homopolymerization of propyleneor copolymerization of propylene and an α-olefin comonomer. In someaspects, the second polyolefin may have a higher molecular weight and/ora higher density than the first polyolefin.

In some embodiments, the second polyolefin may have a molecular weightdistribution M_(w)/M_(n) of less than or equal to about 5, less than orequal to about 4, from about 1 to about 3.5, or from about 1 to about 3.

The second polyolefin may be present in an amount of from greater than 0wt % to about 100 wt % of the composition. In some embodiments, theamount of polyolefin elastomer is from about 30 wt % to about 70 wt %.In some embodiments, the second polyolefin fed to the extruder caninclude from about 10 wt % to about 50 wt % polypropylene, from about 20wt % to about 40 wt % polypropylene, or from about 25 wt % to about 35wt % polypropylene. The polypropylene may be a homopolymer or acopolymer.

The second polyolefin may have a melt viscosity in the range of fromabout 2,000 cP to about 50,000 cP as measured using a Brookfieldviscometer at a temperature of about 177° C. In some embodiments, themelt viscosity is from about 4,000 cP to about 40,000 cP, including fromabout 5,000 cP to about 30,000 cP and from about 6,000 cP to about18,000 cP.

The second polyolefin may have a melt index (T2), measured at 190° C.under a 2.16 kg load, of from about 20.0 g/10 min to about 3,500 g/10min, including from about 250 g/10 min to about 1,900 g/10 min and fromabout 300 g/10 min to about 1,500 g/10 min. In some embodiments, thepolyolefin has a fractional melt index of from 0.5 g/10 min to about3,500 g/10 min.

In some aspects, the density of the second polyolefin is less than 0.90g/cm³, less than about 0.89 g/cm³, less than about 0.88 g/cm³, less thanabout 0.87 g/cm³, less than about 0.86 g/cm³, less than about 0.85g/cm³, less than about 0.84 g/cm³, less than about 0.83 g/cm³, less thanabout 0.82 g/cm³, less than about 0.81 g/cm³, or less than about 0.80g/cm³. In other aspects, the density of the first polyolefin may be fromabout 0.85 g/cm³ to about 0.89 g/cm³, from about 0.85 g/cm³ to about0.88 g/cm³, from about 0.84 g/cm³ to about 0.88 g/cm³, or from about0.83 g/cm³ to about 0.87 g/cm³. In still other aspects, the density isat about 0.84 g/cm³, about 0.85 g/cm³, about 0.86 g/cm³, about 0.87g/cm³, about 0.88 g/cm³, or about 0.89 g/cm³.

The percent crystallinity of the second polyolefin may be less thanabout 60%, less than about 50%, less than about 40%, less than about35%, less than about 30%, less than about 25%, or less than about 20%.The percent crystallinity may be at least about 10%. In some aspects,the crystallinity is in the range of from about 2% to about 60%.

As noted, the silane-crosslinked polyolefin elastomers or blends, e.g.,as employed in roofing membranes 10 (e.g., within the top and bottomlayers 14, 38 as shown in FIG. 1), includes both the first polyolefinand the second polyolefin. The second polyolefin is generally used tomodify the hardness and/or processability of the first polyolefin havinga density less than 0.90 g/cm³. In some aspects, more than just thefirst and second polyolefins may be used to form the silane-crosslinkedpolyolefin elastomer or blend. For example, in some aspects, one, two,three, four, or more different polyolefins having a density less than0.90 g/cm³, less than 0.89 g/cm³, less than 0.88 g/cm³, less than 0.87g/cm³, less than 0.86 g/cm³, or less than 0.85 g/cm³ may be substitutedand/or used for the first polyolefin. In some aspects, one, two, three,four, or more different polyolefins, polyethylene-co-propylenecopolymers may be substituted and/or used for the second polyolefin.

The blend of the first polyolefin having a density less than 0.90 g/cm³and the second polyolefin having a crystallinity less than 40% is usedbecause the subsequent silane grafting and crosslinking of these firstand second polyolefin materials together are what form the core resinstructure in the final silane-crosslinked polyolefin elastomer. Althoughadditional polyolefins may be added to the blend of the silane-grafted,silane-crosslinkable, and/or silane-crosslinked polyolefin elastomer asfillers to improve and/or modify the Young's modulus as desired for thefinal product, any polyolefins added to the blend having a crystallinityequal to or greater than 40% are not chemically or covalentlyincorporated into the crosslinked structure of the finalsilane-crosslinked polyolefin elastomer.

In some aspects, the first and second polyolefins may further includeone or more TPVs and/or EPDM with or without silane graft moieties wherethe TPV and/or EPDM polymers are present in an amount of up to 20 wt %of the silane-crosslinker polyolefin elastomer/blend.

Grafting Initiator

A grafting initiator (also referred to as “a radical initiator” in thedisclosure) can be utilized in the grafting process of at least thefirst and second polyolefins by reacting with the respective polyolefinsto form a reactive species that can react and/or couple with the silanecrosslinker molecule. The grafting initiator can include halogenmolecules, azo compounds (e.g., azobisisobutyl), carboxylic peroxyacids,peroxyesters, peroxyketals, and peroxides (e.g., alkyl hydroperoxides,dialkyl peroxides, and diacyl peroxides). In some embodiments, thegrafting initiator is an organic peroxide selected from di-t-butylperoxide, t-butyl cumyl peroxide, dicumyl peroxide,2,5-dimethyl-2,5-di(t-butyl-peroxy)hexyne-3,1,3-bis(t-butyl-peroxy-isopropyl)benzene,n-butyl-4,4-bis(t-butyl-peroxy)valerate, benzoyl peroxide,t-butylperoxybenzoate, t-butylperoxy isopropyl carbonate, andt-butylperbenzoate, as well as bis(2-methylbenzoyl)peroxide,bis(4-methylbenzoyl)peroxide, t-butyl peroctoate, cumene hydroperoxide,methyl ethyl ketone peroxide, lauryl peroxide, tert-butyl peracetate,di-t-amyl peroxide, t-amyl peroxybenzoate,1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane,α,α′-bis(t-butylperoxy)-1,3-diisopropylbenzene,α,α′-bis(t-butylpexoxy)-1,4-diisopropylbenzene,2,5-bis(t-butylperoxy)-2,5-dimethylhexane, and2,5-bis(t-butylperoxy)-2,5-dimethyl-3-hexyne and 2,4-dichlorobenzoylperoxide. Exemplary peroxides include those sold under the tradenameLUPEROX™ (available from Arkema, Inc.).

In some aspects, the grafting initiator is present in an amount of fromgreater than 0 wt % to about 2 wt % of the composition, including fromabout 0.15 wt % to about 1.2 wt % of the composition. The amount ofinitiator and silane employed may affect the final structure of thesilane grafted polymer (e.g., the degree of grafting in the graftedpolymer and the degree of crosslinking in the cured polymer). In someaspects, the reactive composition contains at least 100 ppm ofinitiator, or at least 300 ppm of initiator. The initiator may bepresent in an amount from 300 ppm to 1500 ppm or from 300 ppm to 2000ppm. The silane:initiator weight ratio may be from about 20:1 to 400:1,including from about 30:1 to about 400:1, from about 48:1 to about350:1, and from about 55:1 to about 333:1.

The grafting reaction can be performed under conditions that optimizegrafts onto the interpolymer backbone while minimizing side reactions(e.g., the homopolymerization of the grafting agent). The graftingreaction may be performed in a melt, in solution, in a solid-state,and/or in a swollen-state. The silanation may be performed in awide-variety of equipment (e.g., twin screw extruders, single screwextruders, Brabenders, internal mixers such as Banbury mixers, and batchreactors). In some embodiments, the polyolefin, silane, and initiatorare mixed in the first stage of an extruder. The melt temperature (i.e.,the temperature at which the polymer starts melting and begins to flow)may be from about 120° C. to about 260° C., including from about 130° C.to about 250° C.

Silane Crosslinker

A silane crosslinker can be used to covalently graft silane moietiesonto the first and second polyolefins and the silane crosslinker mayinclude alkoxysilanes, silazanes, siloxanes, or a combination thereof.The grafting and/or coupling of the various potential silanecrosslinkers or silane crosslinker molecules is facilitated by thereactive species formed by the grafting initiator reacting with therespective silane crosslinker.

In some aspects, the silane crosslinker is a silazane where the silazanemay include, for example, hexamethyldisilazane (HMDS) orBis(trimethylsilyl)amine. In some aspects, the silane crosslinker is asiloxane where the siloxane may include, for example,polydimethylsiloxane (PDMS) and octamethylcyclotetrasiloxane.

In some aspects, the silane crosslinker is an alkoxysilane. As usedherein, the term “alkoxysilane” refers to a compound that comprises asilicon atom, at least one alkoxy group and at least one other organicgroup, wherein the silicon atom is bonded with the organic group by acovalent bond. Preferably, the alkoxysilane is selected fromalkylsilanes; acryl-based silanes; vinyl-based silanes; aromaticsilanes; epoxy-based silanes; amino-based silanes and amines thatpossess —NH₂, —NHCH₃ or —N(CH₃)₂; ureide-based silanes; mercapto-basedsilanes; and alkoxysilanes which have a hydroxyl group (i.e., —OH). Anacryl-based silane may be selected from the group comprisingbeta-acryloxyethyl trimethoxysilane; beta-acryloxy propyltrimethoxysilane; gamma-acryloxyethyl trimethoxysilane;gamma-acryloxypropyl trimethoxysilane; beta-acryloxyethyltriethoxysilane; beta-acryloxypropyl triethoxysilane;gamma-acryloxyethyl triethoxysilane; gamma-acryloxypropyltriethoxysilane; beta-methacryloxyethyl trimethoxysilane;beta-methacryloxypropyl trimethoxysilane; gamma-methacryloxyethyltrimethoxysilane; gamma-methacryloxypropyl trimethoxysilane;beta-methacryloxyethyl triethoxysilane; beta-methacryloxypropyltriethoxysilane; gamma-methacryloxyethyl triethoxysilane;gamma-methacryloxypropyl triethoxysilane; 3-methacryloxypropylmethyldiethoxysilane. A vinyl-based silane may be selected from the groupcomprising vinyl trimethoxysilane; vinyl triethoxysilane; p-styryltrimethoxysilane, methylvinyldimethoxysilane,vinyldimethylmethoxysilane, divinyldimethoxysilane,vinyltris(2-methoxyethoxy)silane, andvinylbenzylethylenediaminopropyltrimethoxysilane. An aromatic silane maybe selected from phenyltrimethoxysilane and phenyltriethoxysilane. Anepoxy-based silane may be selected from the group comprising3-glycydoxypropyl trimethoxysilane; 3-glycydoxypropylmethyldiethoxysilane; 3-glycydoxypropyl triethoxysilane;2-(3,4-epoxycyclohexyl)ethyl trimethoxysilane, andglycidyloxypropylmethyldimethoxysilane. An amino-based silane may beselected from the group comprising 3-aminopropyl triethoxysilane;3-aminopropyl trimethoxysilane; 3-aminopropyldimethyl ethoxysilane;3-aminopropylmethyldiethoxysilane; 4-aminobutyltriethoxysilane;3-aminopropyldiisopropyl ethoxysilane;1-amino-2-(dimethylethoxysilyl)propane;(aminoethylamino)-3-isobutyldimethyl methoxysilane;N-(2-aminoethyl)-3-aminoisobutylmethyl dimethoxysilane;(aminoethylaminomethyl)phenetyl trimethoxysilane;N-(2-aminoethyl)-3-aminopropylmethyl dimethoxysilane;N-(2-aminoethyl)-3-aminopropyl trimethoxysilane;N-(2-aminoethyl)-3-aminopropyl triethoxysilane;N-(6-aminohexyl)aminomethyl trimethoxysilane;N-(6-aminohexyl)aminomethyl trimethoxysilane;N-(6-aminohexyl)aminopropyl trimethoxysilane;N-(2-aminoethyl)-1,1-aminoundecyl trimethoxysilane; 1,1-aminoundecyltriethoxysilane; 3-(m-aminophenoxy)propyl trimethoxysilane;m-aminophenyl trimethoxysilane; p-aminophenyl trimethoxysilane;(3-trimethoxysilylpropyl)diethylenetriamine; N-methylaminopropylmethyldimethoxysilane; N-methylaminopropyl trimethoxysilane;dimethylaminomethyl ethoxysilane;(N,N-dimethylaminopropyl)trimethoxysilane;(N-acetylglycysil)-3-aminopropyl trimethoxysilane,N-phenyl-3-aminopropyltrimethoxysilane,N-phenyl-3-aminopropyltriethoxysilane,phenylaminopropyltrimethoxysilane,aminoethylaminopropyltrimethoxysilane, andaminoethylaminopropylmethyldimethoxysilane. An ureide-based silane maybe 3-ureidepropyl triethoxysilane. A mercapto-based silane may beselected from the group comprising 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyl trimethoxysilane, and 3-mercaptopropyltriethoxysilane. An alkoxysilane having a hydroxyl group may be selectedfrom the group comprising hydroxymethyl triethoxysilane;N-(hydroxyethyl)-N-methylaminopropyl trimethoxysilane;bis(2-hydroxyethyl)-3-aminopropyl triethoxysilane;N-(3-triethoxysilylpropyl)-4-hydroxy butylamide;1,1-(triethoxysilyl)undecanol; triethoxysilyl undecanol; ethylene glycolacetal; and N-(3-ethoxysilylpropyl)gluconamide.

In some aspects, the alkylsilane may be expressed with a generalformula: R_(n)Si(OR′)_(4-n) wherein: n is 1, 2 or 3; R is a C₁₋₂₀ alkylor a C₂₋₂₀ alkenyl; and R′ is an C₁₋₂₀ alkyl. The term “alkyl” by itselfor as part of another substituent, refers to a straight, branched orcyclic saturated hydrocarbon group joined by single carbon-carbon bondshaving 1 to 20 carbon atoms, for example 1 to 10 carbon atoms, forexample 1 to 8 carbon atoms, preferably 1 to 6 carbon atoms. When asubscript is used herein following a carbon atom, the subscript refersto the number of carbon atoms that the named group may contain. Thus,for example, C₁₋₆ alkyl means an alkyl of one to six carbon atoms.Examples of alkyl groups are methyl, ethyl, propyl, isopropyl, butyl,isobutyl, sec-butyl, f-butyl, 2-methylbutyl, pentyl, iso-amyl and itsisomers, hexyl and its isomers, heptyl and its isomers, octyl and itsisomer, decyl and its isomer, dodecyl and its isomers. The term “C₂₋₂₀alkenyl” by itself or as part of another substituent, refers to anunsaturated hydrocarbyl group, which may be linear, or branched,comprising one or more carbon-carbon double bonds having 2 to 20 carbonatoms. Examples of C₂₋₆ alkenyl groups are ethenyl, 2-propenyl,2-butenyl, 3-butenyl, 2-pentenyl and its isomers, 2-hexenyl and itsisomers, 2,4-pentadienyl and the like.

In some aspects, the alkylsilane may be selected from the groupcomprising methyltrimethoxysilane; methyltriethoxysilane;ethyltrimethoxysilane; ethyltriethoxysilane; propyltrimethoxysilane;propyltriethoxysilane; hexyltrimethoxysilane; hexyltriethoxysilane;octyltrimethoxysilane; octyltriethoxysilane; decyltrimethoxysilane;decyltriethoxysilane; dodecyltrimethoxysilane: dodecyltriethoxysilane;tridecyltrimethoxysilane; dodecyltriethoxysilane;hexadecyltrimethoxysilane; hexadecyltriethoxysilane;octadecyltrimethoxysilane; octadecyltriethoxysilane,trimethylmethoxysilane, methylhydrodimethoxysilane,dimethyldimethoxysilane, diisopropyldimethoxysilane,diisobutyldimethoxysilane, isobutyltrimethoxysilane,n-butyltrimethoxysilane, n-butylmethyldimethoxysilane,phenyltrimethoxysilane, phenyltrimethoxysilane,phenylmethyldimethoxysilane, triphenylsilanol, n-hexyltrimethoxysilane,n-octyltrimethoxysilane, isooctyltrimethoxysilane,decyltrimethoxysilane, hexadecyltrimethoxysilane,cyclohexylmethyldimethoxysilane, cyclohexylethyldimethoxysilane,dicyclopentyldimethoxysilane, tert-butylethyldimethoxysilane,tert-butylpropyldimethoxysilane, dicyclohexyldimethoxysilane, and acombination thereof.

In some aspects, the alkylsilane compound may be selected fromtriethoxyoctylsilane, trimethoxyoctylsilane, and a combination thereof.

Additional examples of silanes that can be used as silane crosslinkersinclude, but are not limited to, those of the general formulaCH₂═CR—(COO)_(x)(C_(n)H_(2n))_(y)SiR′₃, wherein R is a hydrogen atom ormethyl group; x is 0 or 1; y is 0 or 1; n is an integer from 1 to 12;each R′ can be an organic group and may be independently selected froman alkoxy group having from 1 to 12 carbon atoms (e.g., methoxy, ethoxy,butoxy), aryloxy group (e.g., phenoxy), araloxy group (e.g., benzyloxy),aliphatic acyloxy group having from 1 to 12 carbon atoms (e.g.,formyloxy, acetyloxy, propanoyloxy), amino or substituted amino groups(e.g., alkylamino, arylamino), or a lower alkyl group having 1 to 6carbon atoms. x and y may both equal 1. In some aspects, no more thanone of the three R′ groups is an alkyl. In other aspects, not more thantwo of the three R′ groups is an alkyl.

Any silane or mixture of silanes known in the art that can effectivelygraft to and crosslink an olefin polymer can be used in the practice ofthe present disclosure. In some aspects, the silane crosslinker caninclude, but is not limited to, unsaturated silanes which include anethylenically unsaturated hydrocarbyl group (e.g., a vinyl, allyl,isopropenyl, butenyl, cyclohexenyl or a gamma-(meth)acryloxy allylgroup) and a hydrolyzable group (e.g., a hydrocarbyloxy,hydrocarbonyloxy, or hydrocarbylamino group). Non-limiting examples ofhydrolyzable groups include, but are not limited to, methoxy, ethoxy,formyloxy, acetoxy, proprionyloxy, and alkyl, or arylamino groups. Inother aspects, the silane crosslinkers are unsaturated alkoxy silaneswhich can be grafted onto the polymer. In still other aspects,additional exemplary silane crosslinkers include vinyltrimethoxysilane,vinyltriethoxysilane, 3-(trimethoxysilyl)propyl methacrylategamma-(meth)acryloxypropyl trimethoxysilane), and mixtures thereof.

The silane crosslinker may be present in the silane-grafted polyolefinelastomer in an amount of from greater than 0 wt % to about 10 wt %,including from about 0.5 wt % to about 5 wt %. The amount of silanecrosslinker may be varied based on the nature of the olefin polymer, thesilane itself, the processing conditions, the grafting efficiency, theapplication, and other factors. The amount of silane crosslinker may beat least 2 wt %, including at least 4 wt % or at least 5 wt %, based onthe weight of the reactive composition. In other aspects, the amount ofsilane crosslinker may be at least 10 wt %, based on the weight of thereactive composition. In still other aspects, the silane crosslinkercontent is at least 1% based on the weight of the reactive composition.In some embodiments, the silane crosslinker fed to the extruder mayinclude from about 0.5 wt % to about 10 wt % of silane monomer, fromabout 1 wt % to about 5 wt % silane monomer, or from about 2 wt % toabout 4 wt % silane monomer.

Condensation Catalyst

A condensation catalyst can facilitate both the hydrolysis andsubsequent condensation of the silane grafts on the silane-graftedpolyolefin elastomer to form crosslinks. In some aspects, thecrosslinking can be aided by the use of an electron beam radiation. Insome aspects, the condensation catalyst can include, for example,organic bases, carboxylic acids, and organometallic compounds (e.g.,organic titanates and complexes or carboxylates of lead, cobalt, iron,nickel, zinc, and tin). In other aspects, the condensation catalyst caninclude fatty acids and metal complex compounds such as metalcarboxylates; aluminum triacetyl acetonate, iron triacetyl acetonate,manganese tetraacetyl acetonate, nickel tetraacetyl acetonate, chromiumhexaacetyl acetonate, titanium tetraacetyl acetonate and cobalttetraacetyl acetonate; metal alkoxides such as aluminum ethoxide,aluminum propoxide, aluminum butoxide, titanium ethoxide, titaniumpropoxide and titanium butoxide; metal salt compounds such as sodiumacetate, tin octylate, lead octylate, cobalt octylate, zinc octylate,calcium octylate, lead naphthenate, cobalt naphthenate, dibutyltindioctoate, dibutyltin dilaurate, dibutyltin maleate and dibutyltindi(2-ethylhexanoate); acidic compounds such as formic acid, acetic acid,propionic acid, p-toluenesulfonic acid, trichloroacetic acid, phosphoricacid, monoalkylphosphoric acid, dialkylphosphoric acid, phosphate esterof p-hydroxyethyl (meth)acrylate, monoalkylphosphorous acid anddialkylphosphorous acid; acids such as p-toluenesulfonic acid, phthalicanhydride, benzoic acid, benzenesulfonic acid, dodecylbenzenesulfonicacid, formic acid, acetic acid, itaconic acid, oxalic acid and maleicacid, ammonium salts, lower amine salts or polyvalent metal salts ofthese acids, sodium hydroxide, lithium chloride; organometal compoundssuch as diethyl zinc and tetra(n-butoxy)titanium; and amines such asdicyclohexylamine, triethylamine, N,N-dimethylbenzylamine,N,N,N′,N′-tetramethyl-1,3-butanediamine, diethanolamine, triethanolamineand cyclohexylethylamine. In still other aspects, the condensationcatalyst can include ibutyltindilaurate, dioctyltinmaleate,dibutyltindiacetate, dibutyltindioctoate, stannous acetate, stannousoctoate, lead naphthenate, zinc caprylate, and cobalt naphthenate.Depending on the desired final material properties of thesilane-crosslinked polyolefin elastomer or blend, a single condensationcatalyst or a mixture of condensation catalysts may be utilized. Thecondensation catalyst(s) may be present in an amount of from about 0.01wt % to about 1.0 wt %, including from about 0.25 wt % to about 8 wt %,based on the total weight of the silane-grafted polyolefinelastomer/blend composition.

In some aspects, a crosslinking system can include and use one or all ofa combination of radiation, heat, moisture, and additional condensationcatalyst. In some aspects, the condensation catalyst may be present inan amount of from 0.25 wt % to 8 wt %. In other aspects, thecondensation catalyst may be included in an amount of from about 1 wt %to about 10 wt % or from about 2 wt % to about 5 wt %.

Optional Additional Components

The silane-crosslinked polyolefin elastomer may optionally include oneor more fillers. The filler(s) may be extruded with the silane-graftedpolyolefin and in some aspects may include additional polyolefins havinga crystallinity greater than 20%, greater than 30%, greater than 40%, orgreater than 50%. In some aspects, the filler(s) may include metaloxides, metal hydroxides, metal carbonates, metal sulfates, metalsilicates, clays, talcs, carbon black, and silicas. Depending on theapplication and/or desired properties, these materials may be fumed orcalcined.

With further regard to the fillers, the metal of the metal oxide, metalhydroxide, metal carbonate, metal sulfate, or metal silicate may beselected from alkali metals (e.g., lithium, sodium, potassium, rubidium,caesium, and francium); alkaline earth metals (e.g., beryllium,magnesium, calcium, strontium, barium, and radium); transition metals(e.g., zinc, molybdenum, cadmium, scandium, titanium, vanadium,chromium, manganese, iron, cobalt, nickel, copper, yttrium, zirconium,niobium, technetium, ruthernium, rhodium, palladium, silver, hafnium,taltalum, tungsten, rhenium, osmium, indium, platinum, gold, mercury,rutherfordium, dubnium, seaborgium, bohrium, hassium, and copernicium);post-transition metals (e.g., aluminum, gallium, indium, tin, thallium,lead, bismuth, and polonium); lanthanides (e.g., lanthanum, cerium,praseodymium, neodymium, promethium, samarium, europium, gadolinium,terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium);actinides (e.g., actinium, thorium, protactinium, uranium, neptunium,plutonium, americium, curium, berkelium, californium, einsteinium,fermium, mendelevium, nobelium, and lawrencium); germanium; arsenic;antimony; and astatine.

The filler(s) of the silane-crosslinked polyolefin elastomer or blendmay be present in an amount of from greater than 0 wt % to about 50 wt%, including from about 1 wt % to about 20 wt %, and from about 3 wt %to about 10 wt %.

The silane-crosslinked polyolefin elastomer and/or the respectivearticles formed (e.g., single ply roofing membranes 10 as depicted inFIG. 1) may also include waxes (e.g., paraffin waxes, microcrystallinewaxes, HDPE waxes, LDPE waxes, thermally degraded waxes, byproductpolyethylene waxes, optionally oxidized Fischer-Tropsch waxes, andfunctionalized waxes). In some embodiments, the wax(es) are present inan amount of from about 0 wt % to about 10 wt %.

Tackifying resins (e.g., aliphatic hydrocarbons, aromatic hydrocarbons,modified hydrocarbons, terpens, modified terpenes, hydrogenatedterpenes, rosins, rosin derivatives, hydrogenated rosins, and mixturesthereof) may also be included in the silane-crosslinker polyolefinelastomer/blend. The tackifying resins may have a ring and ballsoftening point in the range of from 70° C. to about 150° C. and aviscosity of less than about 3,000 cP at 177° C. In some aspects, thetackifying resin(s) are present in an amount of from about 0 wt % toabout 10 wt %.

In some aspects, the silane-crosslinker polyolefin elastomer may includeone or more oils. Non-limiting types of oils include white mineral oilsand naphthenic oils. In some embodiments, the oil(s) are present in anamount of from about 0 wt % to about 10 wt %.

In some aspects, the silane-crosslinked polyolefin elastomer may includeone or more filler polyolefins having a crystallinity greater than 20%,greater than 30%, greater than 40%, or greater than 50%. The fillerpolyolefin may include polypropylene, poly(ethylene-co-propylene),and/or other ethylene/α-olefin copolymers. In some aspects, the use ofthe filler polyolefin may be present in an amount of from about 5 wt %to about 60 wt %, from about 10 wt % to about 50 wt %, from about 20 wt% to about 40 wt %, or from about 5 wt % to about 20 wt %. The additionof the filler polyolefin may increase the Young's modulus by at least10%, by at least 25%, or by at least 50% for the finalsilane-crosslinked polyolefin elastomer.

In some aspects, the silane-crosslinker polyolefin elastomer of thepresent disclosure may include one or more stabilizers (e.g.,antioxidants). The silane-crosslinked polyolefin elastomer may betreated before grafting, after grafting, before crosslinking, and/orafter crosslinking. Other additives may also be included. Non-limitingexamples of additives include antistatic agents, dyes, pigments, UVlight absorbers, nucleating agents, fillers, slip agents, plasticizers,fire retardants, lubricants, processing aides, smoke inhibitors,anti-blocking agents, and viscosity control agents. The antioxidant(s)may be present in an amount of less than 0.5 wt %, including less than0.2 wt % of the composition.

In some aspects, titanium dioxide, a white pigment, may be added to theformulation to provide opacity and color. In addition, the titaniumdioxide also may provide ultraviolet light protection. In some aspects,the titanium dioxide may be pre-blended with the first and/or secondpolyolefins (of the type set forth above) to ensure complete dispersalof the titanium dioxide throughout the composition. In some aspects, toensure complete dispersal of the titanium dioxide into the compositionprior to extrusion or other formation techniques, the titanium dioxidemay be pre-blended with the first and/or second polyolefins in an amountup to 30 wt %, up to 20 wt %, or up to 10 wt %.

Method for Making the Silane-Grafted Polyolefin Elastomer

The synthesis/production of the silane-crosslinked polyolefin elastomermay be performed by combining the respective components in one extruderusing a single-step Monosil process or in two extruders using a two-stepSioplas process, which eliminates the need for additional steps ofmixing and shipping rubber compounds prior to extrusion.

Referring now to FIG. 2, the general chemical process used during boththe single-step Monosil process and two-step Sioplas process used tosynthesize the silane-crosslinked polyolefin elastomer is provided. Theprocess starts with a grafting step that includes initiation from agrafting initiator followed by propagation and chain transfer with thefirst and second polyolefins. The grafting initiator, in some aspects aperoxide or azo compound, homolytically cleaves to form two radicalinitiator fragments that transfer to one of the first and secondpolyolefins chains through a propagation step. The free radical, nowpositioned on the first or second polyolefin chain, can then transfer toa silane molecule and/or another polyolefin chain. Once the initiatorand free radicals are consumed, the silane grafting reaction for thefirst and second polyolefins is complete.

Still referring to FIG. 2, once the silane grafting reaction iscomplete, a mixture of stable first and second silane-graftedpolyolefins is produced. A crosslinking catalyst may then be added tothe first and second silane-grafted polyolefins to form thesilane-grafted polyolefin elastomer. The crosslinking catalyst may firstfacilitate the hydrolysis of the silyl group grafted onto the polyolefinbackbones to form reactive silanol groups. The silanol groups may thenreact with other silanol groups on other polyolefin molecules to form acrosslinked network of elastomeric polyolefin polymer chains linkedtogether through siloxane linkages. The density of silane crosslinksthroughout the silane-grafted polyolefin elastomer can influence thematerial properties exhibited by the elastomer.

Referring now to FIGS. 3 and 4A, a method 200 for making the roofingmembrane 10, using the two-step Sioplas process is shown. The method 200may begin with a step 204 that includes extruding (e.g., with a twinscrew extruder 252) a first polyolefin 240 having a density less than0.86 g/cm³, a second polyolefin 244, and a silan cocktail 248 includingthe silane crosslinker (e.g., vinyltrimethoxy silane, VTMO) and thegrafting initiator (e.g. dicumyl peroxide) together to form asilane-grafted polyolefin blend. The first polyolefin 240 and secondpolyolefin 244 may be added to a reactive twin screw extruder 252 usingan addition hopper 256. The silan cocktail 248 may be added to the twinscrews 260 further down the extrusion line to help promote better mixingwith the blend of the first and second polyolefins 240, 244. A forcedvolatile organic compound (VOC) vacuum 264 may be used on the reactivetwin screw extruder 252 to help maintain a desired reaction pressure.The twin screw extruder 252 is considered reactive because the radicalinitiator and silane crosslinker are reacting with and forming newcovalent bonds with both the first and second polyolefins 240, 244. Themelted silane-grafted polyolefin blend can exit the reactive twin screwextruder 252 using a gear pump 268 that injects the moltensilane-grafted polyolefin blend into a water pelletizer 272 that canform a pelletized silane-grafted polyolefin blend 276. In some aspects,the molten silane-grafted polyolefin blend 276 may be extruded intopellets, pillows, or any other configuration prior to the incorporationof the condensation catalyst 280 (see FIG. 4B) and formation of thefinal article (e.g., a roofing membrane 10 as depicted in FIG. 1).

The reactive twin screw extruder 252 can be configured to have aplurality of different temperature zones (e.g., Z0-Z12 as shown in FIG.4A) that extend for various lengths of the twin screw extruder 252. Insome aspects, the respective temperature zones may have temperaturesranging from about room temperature to about 180° C., from about 120° C.to about 170° C., from about 120° C. to about 160° C., from about 120°C. to about 150° C., from about 120° C. to about 140° C., from about120° C. to about 130° C., from about 130° C. to about 170° C., fromabout 130° C. to about 160° C., from about 130° C. to about 150° C.,from about 130° C. to about 140° C., from about 140° C. to about 170°C., from about 140° C. to about 160° C., from about 140° C. to about150° C., from about 150° C. to about 170° C., and from about 150° C. toabout 160° C. In some aspects, Z0 may have a temperature from about 60°C. to about 110° C. or no cooling; Z1 may have a temperature from about120° C. to about 130° C.; Z2 may have a temperature from about 140° C.to about 150° C.; Z3 may have a temperature from about 150° C. to about160° C.; Z4 may have a temperature from about 150° C. to about 160° C.;Z5 may have a temperature from about 150° C. to about 160° C.; Z6 mayhave a temperature from about 150° C. to about 160° C.; Z7 may have atemperature from about 150° C. to about 160° C.; and Z8-Z12 may have atemperature from about 150° C. to about 160° C.

In some aspects, the number average molecular weight of thesilane-grafted polyolefin elastomers may be in the range of from about4,000 g/mol to about 30,000 g/mol, including from about 5,000 g/mol toabout 25,000 g/mol and from about 6,000 g/mol to about 14,000 g/mol. Theweight average molecular weight of the grafted polymers may be fromabout 8,000 g/mol to about 60,000 g/mol, including from about 10,000g/mol to about 30,000 g/mol.

Referring now to FIGS. 3 and 4B, the method 200 next includes a step 208of extruding the silane-grafted polyolefin blend 276 and thecondensation catalyst 280 together to form a silane-crosslinkablepolyolefin blend 298. In some aspects, one or more optional additives284 may be added with the silane-grafted polyolefin blend 276 and thecondensation catalyst 280 to adjust the final material properties of thesilane-crosslinkable polyolefin blend 298. In step 208, thesilane-grafted polyolefin blend 276 is mixed with a silanol formingcondensation catalyst 280 to form reactive silanol groups on the silanegrafts that can subsequently crosslink when exposed to humidity and/orheat. In some aspects, the condensation catalyst 280 can include amixture of sulfonic acid, antioxidant, process aide, and carbon blackfor coloring where the ambient moisture is sufficient for thiscondensation catalyst 280 to crosslink the silane-crosslinkablepolyolefin blend 298 over a longer time period (e.g., about 48 hours).The silane-grafted polyolefin blend 276 and the condensation catalyst280 may be added to a reactive single screw extruder 288 using anaddition hopper (similar to addition hopper 256 shown in FIG. 4A) and anaddition gear pump 296. The combination of the silane-grafted polyolefinblend 276 and the condensation catalyst 280, and in some aspects one ormore optional additives 284, may be added to a single screw 292 of thereactive single screw extruder 288. The single screw extruder 288 isconsidered reactive because the silane-grafted polyolefin blend 276 andthe condensation catalyst 280 are melted and combined together to mixthe condensation catalyst 280 thoroughly and evenly throughout themelted silane-grafted polyolefin blend 276. The meltedsilane-crosslinkable polyolefin blend 298, as formed in step 208, canexit the reactive single screw extruder 288 through a die that caninject the molten silane-crosslinkable polyolefin blend 298 into theform of an uncured roofing membrane element.

During step 208, as the silane-grafted polyolefin blend 276 is extrudedtogether with the condensation catalyst 280 to form thesilane-crosslinkable polyolefin blend 298, a certain amount ofcrosslinking may occur. In some aspects, the silane-crosslinkablepolyolefin blend 298 may be about 25% cured, about 30% cured, about 35%cured, about 40% cured, about 45% cured, about 50% cured, about 55%cured, about 60% cured, bout 65% cured, or about 70% cured, where a geltest (ASTM D2765) can be used to determine the amount of crosslinking inthe final silane-crosslinked polyolefin elastomer.

Referring to FIGS. 3 and 4B, the method 200 further includes a step 212of extruding and/or calendaring the silane-crosslinkable polyolefinelastomer or blend 298 to form the top and bottom layers 14, 38, ascomprising the uncured silane-crosslinkable polyolefin elastomer. Thesilane-crosslinkable polyolefin elastomer or blend 298 is in a melted ormolten state where it can flow and be shaped as it exits the reactivesingle screw extruder 288. A calendar system 302 is a device having twoor more rollers (the area between the rollers is called a nip) used toprocess the melted silane-crosslinkable polyolefin elastomer blend 298into a sheet or film. As the melted silane-crosslinkable polyolefinelastomer blend 298 leaves the reactive single screw extruder 288, itforms a pool of silane-crosslinkable polyolefin elastomer 306 at a firstnip point of the calendar system 302. The pool of silane-crosslinkablepolyolefin elastomer 306 is then pressed or rolled into the top orbottom layer 14, 38 respectively. The scrim layer 26 may be added to thetop or bottom layer 14, 38, respectively, at any point during thecalendaring process using a scrim roll 318. The scrim layer 26, ascoupled to the top or bottom layer 14, 38, forms a partial scrimmembrane 322. The partial scrim membrane 322 may be further calendaredand pressed with the respectively missing top or bottom layer 14, 38 toform the uncured roofing membrane element.

Referring again to FIG. 3, the method 200 can further include a step 216of crosslinking the silane-crosslinkable polyolefin blend 298 or theroofing membrane element in an uncured form at an ambient temperatureand/or an ambient humidity to form the roofing membrane 10 (see FIG. 1)having a density from about 0.85 g/cm³ to about 0.89 g/cm³. Moreparticularly, in this crosslinking process, the water hydrolyzes thesilane of the silane-crosslinkable polyolefin elastomer to produce asilanol. The silanol groups on various silane grafts can then becondensed to form intermolecular, irreversible Si—O—Si crosslink sites.The amount of crosslinked silane groups, and thus the final polymerproperties, can be regulated by controlling the production process,including the amount of catalyst used.

The crosslinking/curing of step 216 of the method 200 (see FIG. 3) mayoccur over a time period of from greater than 0 to about 20 hours. Insome aspects, curing takes place over a time period of from about 1 hourto about 20 hours, 10 hours to about 20 hours, from about 15 hours toabout 20 hours, from about 5 hours to about 15 hours, from about 1 hourto about 8 hours, or from about 3 hours to about 6 hours. Thetemperature during the crosslinking/curing may be about roomtemperature, from about 20° C. to about 25° C., from about 20° C. toabout 150° C., from about 25° C. to about 100° C., or from about 20° C.to about 75° C. The humidity during curing may be from about 30% toabout 100%, from about 40% to about 100%, or from about 50% to about100%.

In some aspects, an extruder setting is used that is capable ofextruding thermoplastic, with long L/D, 30 to 1, at an extruder heatsetting close to TPV processing conditions wherein the extrudatecrosslinks at ambient conditions becoming a thermoset in properties. Inother aspects, this process may be accelerated by steam exposure.Immediately after extrusion, the gel content (also called the crosslinkdensity) may be about 60%, but after 96 hrs at ambient conditions, thegel content may reach greater than about 95%.

In some aspects, one or more reactive single screw extruders 288 may beused to form the uncured roofing membrane element (and correspondingsingle ply roofing membrane 10) that has one or more types ofsilane-crosslinked polyolefin elastomers. For example, in some aspects,one reactive single screw extruder 288 may be used to produce andextrude a first silane-crosslinked polyolefin elastomer associatedemployed in a top layer 14 of a roofing membrane 10 (see FIG. 1), whilea second reactive single screw extruder 288 may be used to produce andextrude a second silane-crosslinked polyolefin elastomer employed in abottom layer 38 of the roofing membrane 10. The complexity, architectureand property requirements of the roofing membrane 10 will determine thenumber and types of reactive single screw extruder 288 necessary tofabricate it.

It is understood that the prior description outlining and teaching thevarious roofing membranes 10, and their respective components andcompositions, can be used in any combination, and applies equally wellto the method 200 for making the roofing membrane 10 using the two-stepSioplas process as shown in FIGS. 3, 4A and 4B.

Referring now to FIGS. 5 and 6, a method 400 for making the roofingmembrane 10 using the one-step Monosil process is shown. The method 400may begin with a step 404 that includes extruding (e.g., with a singlescrew extruder 444) the first polyolefin 240 having a density less than0.86 g/cm³, the second polyolefin 244, the silan cocktail 248 includingthe silane crosslinker (e.g., vinyltrimethoxy silane, VTMO) and graftinginitiator (e.g. dicumyl peroxide), and the condensation catalyst 280together to form the crosslinkable silane-grafted polyolefin blend 298.The first polyolefin 240, second polyolefin 244, and silan cocktail 248may be added to the reactive single screw extruder 444 using an additionhopper 440. In some aspects, the silan cocktail 248 may be added to asingle screw 448 further down the extrusion line to help promote bettermixing with the first and second polyolefin 240, 244 blend. In someaspects, one or more optional additives 284 may be added with the firstpolyolefin 240, second polyolefin 244, condensation catalyst 280 andsilan cocktail 248 to adjust the final material properties of thesilane-crosslinkable polyolefin blend 298. The single screw extruder 444is considered reactive because the grafting initiator and silanecrosslinker of the silan cocktail 248 are reacting with and forming newcovalent bonds with both the first and second polyolefins 240, 244. Inaddition, the reactive single screw extruder 444 mixes the condensationcatalyst 280 in together with the melted silane-grafted polyolefin blendcomprising the first and second polyolefins 240, 244, silan cocktail 248and any optional additives 284. The resulting meltedsilane-crosslinkable polyolefin blend 298 can exit the reactive singlescrew extruder 444 using a gear pump (not shown) and/or die that caneject the molten silane-crosslinkable polyolefin blend 298 into the formof an uncured roofing membrane element.

During step 404, as the first polyolefin 240, second polyolefin 244,silan cocktail 248, and condensation catalyst 280 are extruded together,a certain amount of crosslinking may occur in the reactive single screwextruder 444 to the silane-crosslinkable blend 298. In some aspects, thesilane-crosslinkable polyolefin blend 298 may be about 25% cured, about30% cured, about 35% cured, about 40% cured, about 45% cured, about 50%cured, about 55% cured, about 60% cured, bout 65% cured, or about 70% asit leaves the reactive single screw extruder 444. The gel test (ASTMD2765) can be used to determine the amount of crosslinking in the finalsilane-crosslinked polyolefin elastomer.

The reactive single screw extruder 444 can be configured to have aplurality of different temperature zones (e.g., Z0-Z7 as shown in FIG.6) that extend for various lengths along the extruder. In some aspects,the respective temperature zones may have temperatures ranging fromabout room temperature to about 180° C., from about 120° C. to about170° C., from about 120° C. to about 160° C., from about 120° C. toabout 150° C., from about 120° C. to about 140° C., from about 120° C.to about 130° C., from about 130° C. to about 170° C., from about 130°C. to about 160° C., from about 130° C. to about 150° C., from about130° C. to about 140° C., from about 140° C. to about 170° C., fromabout 140° C. to about 160° C., from about 140° C. to about 150° C.,from about 150° C. to about 170° C., and from about 150° C. to about160° C. In some aspects, Z0 may have a temperature from about 60° C. toabout 110° C. or no cooling; Z1 may have a temperature from about 120°C. to about 130° C.; Z2 may have a temperature from about 140° C. toabout 150° C.; Z3 may have a temperature from about 150° C. to about160° C.; Z4 may have a temperature from about 150° C. to about 160° C.;Z5 may have a temperature from about 150° C. to about 160° C.; Z6 mayhave a temperature from about 150° C. to about 160° C.; and Z7 may havea temperature from about 150° C. to about 160° C.

In some aspects, the number average molecular weight of thesilane-grafted polyolefin elastomers may be in the range of from about4,000 g/mol to about 30,000 g/mol, including from about 5,000 g/mol toabout 25,000 g/mol and from about 6,000 g/mol to about 14,000 g/mol. Theweight average molecular weight of the grafted polymers may be fromabout 8,000 g/mol to about 60,000 g/mol, including from about 10,000g/mol to about 30,000 g/mol.

Referring to FIGS. 5 and 6, the method 400 further includes a step 408of extruding and/or calendaring the silane-crosslinkable polyolefinelastomer or blend 298 to form the top and bottom layers 14, 38, ascomprising the uncured silane-crosslinkable polyolefin elastomer. Thesilane-crosslinkable polyolefin elastomer or blend 298 is in a melted ormolten state where it can flow and be shaped as it exits the reactivesingle screw extruder 444. As previously mentioned, the calendar system302 is a device having two or more rollers (the area between the rollersis called a nip) used to process the melted silane-crosslinkablepolyolefin elastomer blend 298 into a sheet or film. As the meltedsilane-crosslinkable polyolefin elastomer blend 298 leaves the reactivesingle screw extruder 444, it forms a pool of silane-crosslinkablepolyolefin elastomer 306 at a first nip point of the calendar system302. The pool of silane-crosslinkable polyolefin elastomer 306 is thenpressed or rolled into the top or bottom layer 14, 38, respectively. Thescrim layer 26 may be added to the top or bottom layer 14, 38respectively at any point during the calendaring process using a scrimroll 318. The scrim layer 26, as coupled to the top or bottom layer 14,38, forms a partial scrim membrane 322. The partial scrim membrane 322may be further calendared and pressed with the respectively missing topor bottom layer 14, 38 to form an uncured roofing membrane element.

Still referring to FIG. 5, the method 400 can further include a step 412of crosslinking the silane-crosslinkable polyolefin blend 298 of theuncured roofing membrane element at an ambient temperature and anambient humidity to form the element into the roofing membrane 10 (seeFIG. 1) having a density from about 0.85 g/cm³ to about 0.89 g/cm³. Theamount of crosslinked silane groups, and thus the final polymerproperties of the roofing membrane 10, can be regulated by controllingthe production process, including the amount of catalyst used.

The step 412 of crosslinking the silane-crosslinkable polyolefin blend298 may occur over a time period of from greater than 0 to about 20hours. In some aspects, curing takes place over a time period of fromabout 1 hour to about 20 hours, 10 hours to about 20 hours, from about15 hours to about 20 hours, from about 5 hours to about 15 hours, fromabout 1 hour to about 8 hours, or from about 3 hours to about 6 hours.The temperature during the crosslinking and curing may be about roomtemperature, from about 20° C. to about 25° C., from about 20° C. toabout 150° C., from about 25° C. to about 100° C., or from about 20° C.to about 75° C. The humidity during curing may be from about 30% toabout 100%, from about 40% to about 100%, or from about 50% to about100%.

In some aspects, an extruder setting is used that is capable ofextruding thermoplastic, with long L/D, 30 to 1, at an extruder heatsetting close to TPV processing conditions wherein the extrudatecrosslinks at ambient conditions becoming a thermoset in properties. Inother aspects, this process may be accelerated by steam exposure.Immediately after extrusion, the gel content (also called the crosslinkdensity) may be about 60%, but after 96 hrs at ambient conditions, thegel content may reach greater than about 95%.

In some aspects, one or more reactive single screw extruders 444 may beused to form the roofing membrane 10 that has one or more types ofsilane-crosslinked polyolefin elastomers. For example, in some aspects,one reactive single screw extruder 444 may be used to produce andextrude a first silane-crosslinked polyolefin elastomer associated withthe top layer 14 of the roofing membrane 10 (see FIG. 1), while a secondreactive single screw extruder 444 may be used to produce and extrude asecond silane-crosslinked polyolefin elastomer associated with thebottom layer 38 of the roofing membrane 10. The complexity, architectureand required properties of the final roofing membrane 10 will determinethe number and types of reactive single screw extruders 444 employedaccording to the method 400 depicted in FIG. 5.

It is understood that the prior description outlining and teaching ofthe various roofing membranes 10, and their respective components andcompositions, can be used in any combination, and applies equally wellto the method 400 for making the roofing membrane 10 using the one-stepMonosil process as shown in FIGS. 5 and 6.

Silane-Crosslinked Polyolefin Elastomer Physical Properties

A “thermoplastic”, as used herein, is defined to mean a polymer thatsoftens when exposed to heat and returns to its original condition whencooled to room temperature. A “thermoset”, as used herein, is defined tomean a polymer that solidifies and irreversibly “sets” or “crosslinks”when cured. In either of the Monosil or Sioplas processes describedabove, it is important to understand the careful balance ofthermoplastic and thermoset properties of the various differentmaterials used to produce the final thermoset silane-crosslinkedpolyolefin elastomer or roofing membrane 10. Each of the intermediatepolymer materials mixed and reacted using a reactive twin screwextruder, and/or a reactive single screw extruder are thermosets.Accordingly, the silane-grafted polyolefin blend 276 and thesilane-crosslinkable polyolefin blend 298 are thermoplastics and can besoftened by heating so the respective materials can flow. Once thesilane-crosslinkable polyolefin blend 298 is extruded, molded, pressed,and/or shaped into the uncured roofing membrane element or otherrespective article, the silane-crosslinkable polyolefin blend 298 canbegin to crosslink or cure at an ambient temperature and an ambienthumidity to form the roofing membrane 10 (or other end product form), ascomprising one or more silane-crosslinked polyolefin blends.

The thermoplastic/thermoset behavior of the silane-crosslinkablepolyolefin blend 298 and corresponding silane-crosslinked polyolefinblend are important for the various compositions and articles disclosedherein (e.g., roofing membrane 10 shown in FIG. 1) because of thepotential energy savings provided using these materials. For example, amanufacturer can save considerable amounts of energy by being able tocure the silane-crosslinkable polyolefin blend 298 at an ambienttemperature and an ambient humidity. This curing process is typicallyperformed in the industry by applying significant amounts of energy toheat or steam treat crosslinkable polyolefins 298. The ability to curethe inventive silane-crosslinkable polyolefin blend 298 with ambienttemperature and/or ambient humidity is not a capability necessarilyintrinsic to crosslinkable polyolefins. Rather, this capability orproperty is dependent on the relatively low density of thesilane-crosslinkable polyolefin blend 298. In some aspects, noadditional curing overs, heating ovens, steam ovens, or other forms ofheat producing machinery other than what was provided in the extrudersare used to form the silane-crosslinked polyolefin elastomers.

The specific gravity of the silane-crosslinked polyolefin elastomer ofthe present disclosure may be lower than the specific gravities ofexisting TPV and EPDM formulations used in the art. The reduced specificgravity of these materials can lead to lower weight parts, therebyfacilitating additional ease-of-assembly for roofers and otherindividuals charged with installing the roofing membranes 10 of thedisclosure. For example, the specific gravity of the silane-crosslinkedpolyolefin elastomer of the present disclosure may be from about 0.80g/cm³ to about 1.50 g/cm³, from about 1.25 g/cm³ to about 1.45 g/cm³,from about 1.30 g/cm³ to about 1.40 g/cm³, about 1.25 g/cm³, about 1.30g/cm³, about 1.35 g/cm³, about 1.40 g/cm³, about 1.45 g/cm³, about 1.50g/cm³, less than 1.75 g/cm³, less than 1.60 g/cm³, less than 1.50 g/cm³,or less than 1.45 g/cm³, as compared to conventional TPV materials whichmay have a specific gravity greater than 2.00 g/cm³and conventional EPDMmaterials which may have a specific gravity of from 2.0 g/cm³ to 3.0g/cm³.

The stress/strain behavior of an exemplary silane-crosslinked polyolefinelastomer of the present disclosure (i.e., “silane-crosslinkedpolyolefin elastomer”) relative to two existing EPDM materials isprovided. In particular, FIG. 7 displays a smaller area between thestress/strain curves for the silane-crosslinked polyolefin of thedisclosure (labeled as “Silane Cross-linked Polyolefin Elastomer” inFIG. 7), as compared to the areas between the stress/strain curves ofEPDM compound A and EPDM compound B. This smaller area between thestress/strain curves for the silane-crosslinked polyolefin elastomer canbe desirable for roofing membranes 10. Elastomeric materials typicallyhave non-linear stress/strain curves with a significant loss of energywhen repeatedly stressed. The silane-crosslinked polyolefin elastomersof the present disclosure may exhibit greater elasticity and lessviscoelasticity (e.g., have linear curves and exhibit very low energyloss). Embodiments of the silane-crosslinked polyolefin elastomersdescribed herein do not have any filler or plasticizer incorporated intothese materials so their corresponding stress/strain curves do not haveor display any Mullins effect and/or Payne effect. The lack of Mullinseffect for these silane-crosslinked polyolefin elastomers is due to thelack of any filler or plasticizer added to the silane-crosslinkedpolyolefin blend so the stress/strain curve does not depend on themaximum loading previously encountered where there is no instantaneousand irreversible softening. The lack of Payne effect for thesesilane-crosslinked polyolefin elastomers is due to the lack of anyfiller or plasticizer added to the silane-crosslinked polyolefin blendso the stress/strain curve does not depend on the small strainamplitudes previously encountered where there is no change in theviscoelastic storage modulus based on the amplitude of the strain.

The silane-crosslinked polyolefin elastomer or roofing membrane 10 canexhibit a compression set of from about 5.0% to about 30.0%, from about5.0% to about 25.0%, from about 5.0% to about 20.0%, from about 5.0% toabout 15.0%, from about 5.0% to about 10.0%, from about 10.0% to about25.0%, from about 10.0% to about 20.0%, from about 10.0% to about 15.0%,from about 15.0% to about 30.0%, from about 15.0% to about 25.0%, fromabout 15.0% to about 20.0%, from about 20.0% to about 30.0%, or fromabout 20.0% to about 25.0%, as measured according to ASTM D 395 (22 hrs@ 23° C., 70° C., 80° C., 90° C., 125° C., and/or 175° C.).

In other implementations, the silane-crosslinked polyolefin elastomer orroofing membrane 10 can exhibit a compression set of from about 5.0% toabout 20.0%, from about 5.0% to about 15.0%, from about 5.0% to about10.0%, from about 7.0% to about 20.0%, from about 7.0% to about 15.0%,from about 7.0% to about 10.0%, from about 9.0% to about 20.0%, fromabout 9.0% to about 15.0%, from about 9.0% to about 10.0%, from about10.0% to about 20.0%, from about 10.0% to about 15.0%, from about 12.0%to about 20.0%, or from about 12.0% to about 15.0%, as measuredaccording to ASTM D 395 (22 hrs @ 23° C., 70° C., 80° C., 90° C., 125°C., and/or 175° C.).

The silane-crosslinked polyolefin elastomer or roofing membrane 10 mayexhibit a crystallinity of from about 5% to about 40%, from about 5% toabout 25%, from about 5% to about 15%, from about 10% to about 20%, fromabout 10% to about 15%, or from about 11% to about 14% as determinedusing density measurements, differential scanning calorimetry (DSC),X-Ray Diffraction, infrared spectroscopy, and/or solid state nuclearmagnetic spectroscopy. As disclosed herein, DSC was used to measure theenthalpy of melting in order to calculate the crystallinity of therespective samples.

The silane-crosslinked polyolefin elastomer or roofing membrane 10 mayexhibit a glass transition temperature of from about −75° C. to about−25° C., from about −65° C. to about −40° C., from about −60° C. toabout −50° C., from about −50° C. to about −25° C., from about −50° C.to about −30° C., or from about −45° C. to about −25° C. as measuredaccording to differential scanning calorimetry (DSC) using a secondheating run at a rate of 5° C./min or 10° C./min.

The silane-crosslinked polyolefin elastomer or roofing membrane 10 mayexhibit a weathering color difference of from about 0.25 ΔE to about 2.0ΔE, from about 0.25 ΔE to about 1.5 ΔE, from about 0.25 ΔE to about 1.0ΔE, or from about 0.25 ΔE to about 0.5 ΔE, as measured according to ASTMD2244. In some embodiments, the roofing membrane 10 may be a high-loadflame retardant thermoplastic polyolefin (TPO) having the aboveweathering properties.

EXAMPLES

The following non-limiting examples are provided as exemplaryembodiments to further outline aspects of the disclosure.

Materials

All chemicals, constituents and precursors were obtained from commercialsuppliers and used as provided without further purification.

Example 1 Preparation of the Silane-Grafted Polyolefin Elastomer

Example 1 (Ex. 1) or ED76-4A was produced by extruding 82.55 wt %ENGAGE™ 8842 and 14.45 wt % MOSTEN™ TB 003 together with 3.0 wt % SILANRHS 14/032 or SILFIN 29 to form a silane-grafted polyolefin elastomer,according to one of the foregoing methods outlined in the disclosure.The Example 1 silane-grafted polyolefin elastomer was then extrudedusing various condensation catalysts and fillers to form asilane-crosslinkable polyolefin elastomer, as suitable for top andbottom layers 14, 38 of a roofing membrane (as described below inExample 2). The composition of the Example 1 silane-grafted polyolefinelastomer is provided in Table 1 below.

TABLE 1 Ingredients Example 1 ENGAGE 8842 82.55 MOSTEN TB 003 14.45SILFIN 29 3.00 TOTAL 100

Example 2 Preparation of the Roofing Membrane

In this example, identical top and bottom layers 14, 38 were used toproduce an embodiment of a single ply roofing membrane 10. Inparticular, the top and bottom layers 14 38 were produced by extruding29.0 wt % silane-grafted polyolefin elastomer (from Example 1) and 70.0wt % vinyl silane coated magnesium dihydroxide, Mg(OH)₂ (MDH), togetherwith 1.0 wt % dioctyltin dilaurate (DOTL) condensation catalyst to forma silane-crosslinkable polyolefin elastomer blend. The blend was thenextruded and calendared to provide the respective top and bottom layers14, 38 of an uncured roofing membrane element. The silane-crosslinkablepolyolefin elastomer of the layers 14, 38 of the uncured roofingmembrane element was then cured at ambient temperature and humidity toform the roofing membrane 10. The composition of the roofing membrane 10formed in this example is provided in Table 2 below.

Example 3 Preparation of the Roofing Membrane

In this example, identical top and bottom layers 14, 38 were used toproduce another embodiment of a single ply roofing membrane 10. Inparticular, the top and bottom layers 14, 38 were produced by extruding29.0 wt % silane-grafted polyolefin elastomer (from Example 1) and 70.0wt % stearic acid coated magnesium dihydroxide, Mg(OH)₂ (MDH), togetherwith 1.0 wt % dioctyltin dilaurate (DOTL) condensation catalyst to forma silane-crosslinkable polyolefin elastomer blend. The blend was thenextruded and calendared to provide the respective top and bottom layers14, 38 of an uncured roofing membrane element. The silane-crosslinkablepolyolefin elastomer of the layers 14, 38 of the uncured roofingmembrane element was then cured at ambient temperature and humidity toform the roofing membrane 10. The composition of the roofing membrane 10formed in this example is also provided in Table 2 below.

TABLE 2 Comparison of Roofing Membranes Vinyl Silane Stearic Acid DOTLED 76-4A coated MDH coated MDH Catalyst Example Sample (wt %) (wt %) (wt%) (wt %) Example 2 Top Layer 29 70 — 1 Example 2 Bottom 29 70 — 1 LayerExample 3 Top Layer 29 — 70 1 Example 3 Bottom 29 — 70 1 Layer

Referring now to FIG. 8, the thermal stability of Example 1 is providedwith respect to a comparative EPDM peroxide crosslinked resin and acomparative EPDM sulfur crosslinked resin. As shown, Example 1 canretain nearly 90% of its elastic properties at 150° C. for greater than500 hrs. The retention of elastic properties as provided in Example 1 isrepresentative of each of the inventive silane-crosslinked polyolefinelastomers disclosed herein. The roofing member made from thesesilane-crosslinked polyolefin elastomers may retain up to 60%, 70%, 80%,or 90% of its elastic properties as determined by using StressRelaxation measurements at 150° C. for greater than 100 hrs, greaterthan 200 hrs, greater than 300 hrs, greater than 400 hrs, and greaterthan 500 hrs.

Referring now to FIG. 9, the compression set values are provided acrossa time period of 4,000 hrs for Ex. 1 that demonstrates the superior longterm retention of elastic properties of the silane-crosslinkedpolyolefin elastomer material used to make the roofing membrane 10. Asprovided, the Ex. 1 silane-crosslinked polyolefin elastomer materialmaintains a compression set of 35% or lower as measured according toASTM D 395 (30% @ 110° C.). The ability of these silane-crosslinkedpolyolefin elastomer materials used in roofing membranes 10 to retainits elasticity (compression set %) over a long period of time uponexposure to heat that simulates exterior weathering or aging is providedby this representative example of these roofing membrane 10 materials.

For purposes of this disclosure, the term “coupled” (in all of itsforms, couple, coupling, coupled, etc.) generally means the joining oftwo components directly or indirectly to one another. Such joining maybe stationary in nature or movable in nature. Such joining may beachieved with the two components and any additional intermediate membersbeing integrally formed as a single unitary body with one another orwith the two components. Such joining may be permanent in nature or maybe removable or releasable in nature unless otherwise stated.

It is also important to note that the construction and arrangement ofthe elements of the device as shown in the exemplary embodiments isillustrative only. Although only a few embodiments of the presentinnovations have been described in detail in this disclosure, thoseskilled in the art who review this disclosure will readily appreciatethat many modifications are possible (e.g., variations in sizes,dimensions, structures, shapes and proportions of the various elements,values of parameters, mounting arrangements, use of materials, colors,orientations, etc.) without materially departing from the novelteachings and advantages of the subject matter recited. For example,elements shown as integrally formed may be constructed of multiple partsor elements shown as multiple parts may be integrally formed, theoperation of the interfaces may be reversed or otherwise varied, thelength or width of the structures and/or members or connector or otherelements of the system may be varied, the nature or number of adjustmentpositions provided between the elements may be varied. It should benoted that the elements and/or assemblies of the system may beconstructed from any of a wide variety of materials that providesufficient strength or durability, in any of a wide variety of colors,textures, and combinations. Accordingly, all such modifications areintended to be included within the scope of the present innovations.Other substitutions, modifications, changes, and omissions may be madein the design, operating conditions, and arrangement of the desired andother exemplary embodiments without departing from the spirit of thepresent innovations.

It will be understood that any described processes or steps withindescribed processes may be combined with other disclosed processes orsteps to form structures within the scope of the present device. Theexemplary structures and processes disclosed herein are for illustrativepurposes and are not to be construed as limiting.

The above description is considered that of the illustrated embodimentsonly. Modifications of the device will occur to those skilled in the artand to those who make or use the device. Therefore, it is understoodthat the embodiments shown in the drawings and described above is merelyfor illustrative purposes and not intended to limit the scope of thearticles, processes and compositions, which are defined by the followingclaims as interpreted according to the principles of patent law,including the Doctrine of Equivalents.

LISTING OF NON-LIMITING EMBODIMENTS

Embodiment A is a roofing membrane comprising: a top layer comprising aflame retardant and a first silane-crosslinked polyolefin elastomerhaving a density less than 0.90 g/cm³; a scrim layer; and a bottom layercomprising a flame retardant and a second silane-crosslinked polyolefinelastomer having a density less than 0.90 g/cm³, wherein the top andbottom layers of the single ply roofing membrane both exhibit acompression set of from about 5.0% to about 35.0%, as measured accordingto ASTM D 395 (22 hrs @ 70° C.).

The roofing membrane of Embodiment A wherein the compression set is fromabout 10% to about 30%.

The roofing membrane of Embodiment A or Embodiment A with any of theintervening features wherein the first and second silane-crosslinkedpolyolefin elastomers both exhibit a crystallinity of from about 5% toabout 25%.

The roofing membrane of Embodiment A or Embodiment A with any of theintervening features wherein the first and second silane-crosslinkedpolyolefin elastomers have a glass transition temperature of from about−75° C. to about −25° C.

The roofing membrane of Embodiment A or Embodiment A with any of theintervening features wherein the first and second silane-crosslinkedpolyolefin elastomers each comprise a first polyolefin having a densityless than 0.86 g/cm³, a second polyolefin, a silane crosslinker, agrafting initiator, and a condensation catalyst.

The roofing membrane of Embodiment A or Embodiment A with any of theintervening features wherein the density is from about 0.85 g/cm³ toabout 0.89 g/cm³.

The roofing membrane of Embodiment A or Embodiment A with any of theintervening features wherein the single ply roofing membrane exhibits aweathering color difference of from about 0.25 ΔE to about 2.0 ΔE, asmeasured according to ASTM D2244.

The roofing membrane of Embodiment A or Embodiment A with any of theintervening features wherein the first silane-crosslinked polyolefinelastomer and the second silane-crosslinked polyolefin elastomer arechemically distinct from each other.

Embodiment B is a method of making a roofing membrane, the methodcomprising: extruding a first silane-crosslinkable polyolefin elastomerto form a top layer; extruding a second silane-crosslinkable polyolefinelastomer to form a bottom layer; calendaring a scrim layer between thetop and the bottom layers to form an uncured roofing membrane element;and crosslinking the silane-crosslinkable polyolefin elastomers of thetop and the bottom layers in the uncured roofing membrane element at acuring temperature and a curing humidity to form the single ply roofingmembrane, wherein the top and bottom layers of the single ply roofingmembrane both exhibit a compression set of from about 5.0% to about35.0%, as measured according to ASTM D 395 (22 hrs @ 70° C.).

The method of Embodiment B wherein the first silane-crosslinkablepolyolefin elastomer and the second silane-crosslinkable polyolefinelastomer are chemically distinct from each other.

The method of Embodiment B or Embodiment B with any of the interveningfeatures wherein the curing temperature is an ambient temperature.

The method of Embodiment B or Embodiment B with any of the interveningfeatures wherein the curing humidity is an ambient humidity.

The method of Embodiment B or Embodiment B with any of the interveningfeatures wherein the first and second silane-crosslinkable polyolefinelastomers each comprise a first polyolefin having a density less than0.86 g/cm³, a second polyolefin, a silane crosslinker, a graftinginitiator, and a condensation catalyst.

The method of Embodiment B or Embodiment B with any of the interveningfeatures wherein the single ply roofing membrane exhibits a weatheringcolor difference of from about 0.25 ΔE to about 2.0 ΔE, as measuredaccording to ASTM D2244.

The method of Embodiment B or Embodiment B with any of the interveningfeatures wherein the single ply roofing membrane exhibits a flameretardance rating of classification D as measured in accordance with theEN ISO 11925-2 surface exposure test.

Embodiment C is a method of making a high-load flame retardantthermoplastic polyolefin (TPO) roofing membrane, the method comprising:adding a silane-grafted polyolefin elastomer, a flame retardant, and acondensation catalyst to a reactive single screw extruder to produce asilane-crosslinkable polyolefin elastomer; calendaring thesilane-crosslinkable polyolefin elastomer to form a top layer and abottom layer; calendaring a scrim layer between the top and the bottomlayers to form an uncured roofing membrane element; and crosslinking thesilane-crosslinkable polyolefin elastomers of the top and the bottomlayers in the uncured roofing membrane element at an ambient temperatureand an ambient humidity to form the thermoplastic polyolefin (TPO)roofing membrane, wherein the top and bottom layers of the thermoplasticpolyolefin (TPO) roofing membrane both exhibit a compression set of fromabout 5.0% to about 35.0%, as measured according to ASTM D 395 (22 hrs @70° C.).

The method of Embodiment C wherein the top and bottom layers arechemically equivalent to each other.

The method of Embodiment C or Embodiment C with any of the interveningfeatures wherein the single ply roofing membrane exhibits a flameretardance rating of classification D as measured in accordance with theEN ISO 11925-2 surface exposure test.

The method of Embodiment C or Embodiment C with any of the interveningfeatures wherein the silane-grafted polyolefin elastomer comprises afirst polyolefin having a density less than 0.86 g/cm³, a secondpolyolefin, a silane crosslinker, a grafting initiator.

The method of Embodiment C or Embodiment C with any of the interveningfeatures wherein the high-load flame retardant thermoplastic polyolefin(TPO) roofing membrane exhibits a weathering color difference of fromabout 0.25 ΔE to about 2.0 ΔE, as measured according to ASTM D2244.

What is claimed is:
 1. A roofing membrane comprising: a top layercomprising a flame retardant and a first silane-crosslinked polyolefinelastomer having a density less than 0.90 g/cm³; a scrim layer; and abottom layer comprising a flame retardant and a secondsilane-crosslinked polyolefin elastomer having a density less than 0.90g/cm³, wherein the top and bottom layers of the roofing membrane bothexhibit a compression set of from about 5.0% to about 35.0%, as measuredaccording to ASTM D 395 (22 hrs @ 70° C.).
 2. The roofing membrane ofclaim 1, wherein the compression set is from about 10% to about 30%. 3.The roofing membrane of claim 1, wherein the first and secondsilane-crosslinked polyolefin elastomers both exhibit a crystallinity offrom about 5% to about 25%.
 4. The roofing membrane of claim 1, whereinthe first and second silane-crosslinked polyolefin elastomers have aglass transition temperature of from about −75° C. to about −25° C. 5.The roofing membrane of claim 1, wherein the first and secondsilane-crosslinked polyolefin elastomers each comprise a firstpolyolefin having a density less than 0.86 g/cm³, a second polyolefin, asilane crosslinker, a grafting initiator, and a condensation catalyst.6. The roofing membrane of claim 1, wherein the density is from about0.85 g/cm³ to about 0.89 g/cm³.
 7. The roofing membrane of claim 1,wherein the roofing membrane exhibits a weathering color difference offrom about 0.25 ΔE to about 2.0 ΔE, as measured according to ASTM D2244.8. The roofing membrane of claim 1, wherein the first silane-crosslinkedpolyolefin elastomer and the second silane-crosslinked polyolefinelastomer are chemically distinct from each other.
 9. A method of makinga roofing membrane, the method comprising: extruding a firstsilane-crosslinkable polyolefin elastomer to form a top layer; extrudinga second silane-crosslinkable polyolefin elastomer to form a bottomlayer; calendaring a scrim layer between the top and the bottom layersto form an uncured roofing membrane element; and crosslinking thesilane-crosslinkable polyolefin elastomers of the top and the bottomlayers in the uncured roofing membrane element at a curing temperatureand a curing humidity to form the roofing membrane, wherein the top andbottom layers of the roofing membrane both exhibit a compression set offrom about 5.0% to about 35.0%, as measured according to ASTM D 395 (22hrs @ 70° C.).
 10. The method of claim 9, wherein the firstsilane-crosslinkable polyolefin elastomer and the secondsilane-crosslinkable polyolefin elastomer are chemically distinct fromeach other.
 11. The method of claim 9, wherein the curing temperature isan ambient temperature.
 12. The method of claim 9, wherein the curinghumidity is an ambient humidity.
 13. The method of claim 9, wherein thefirst and second silane-crosslinkable polyolefin elastomers eachcomprise a first polyolefin having a density less than 0.86 g/cm³, asecond polyolefin, a silane crosslinker, a grafting initiator, and acondensation catalyst.
 14. The method of claim 9, wherein the roofingmembrane exhibits a weathering color difference of from about 0.25 ΔE toabout 2.0 ΔE, as measured according to ASTM D2244.
 15. The method ofclaim 9, wherein the roofing membrane exhibits a flame retardance ratingof classification D as measured in accordance with the EN ISO 11925-2surface exposure test.
 16. A method of making a high-load flameretardant thermoplastic polyolefin (TPO) roofing membrane, the methodcomprising: adding a silane-grafted polyolefin elastomer, a flameretardant, and a condensation catalyst to a reactive single screwextruder to produce a silane-crosslinkable polyolefin elastomer;calendaring the silane-crosslinkable polyolefin elastomer to form a toplayer and a bottom layer; calendaring a scrim layer between the top andthe bottom layers to form an uncured roofing membrane element; andcrosslinking the silane-crosslinkable polyolefin elastomers of the topand the bottom layers in the uncured roofing membrane element at anambient temperature and an ambient humidity to form the thermoplasticpolyolefin (TPO) roofing membrane, wherein the top and bottom layers ofthe thermoplastic polyolefin (TPO) roofing membrane both exhibit acompression set of from about 5.0% to about 35.0%, as measured accordingto ASTM D 395 (22 hrs @ 70° C.).
 17. The method of claim 16, wherein thetop and bottom layers are chemically equivalent to each other.
 18. Themethod of claim 16, wherein the single ply roofing membrane exhibits aflame retardance rating of classification D as measured in accordancewith the EN ISO 11925-2 surface exposure test.
 19. The method of claim16, wherein the silane-grafted polyolefin elastomer comprises a firstpolyolefin having a density less than 0.86 g/cm³, a second polyolefin, asilane crosslinker, a grafting initiator.
 20. The method of claim 16,wherein the high-load flame retardant thermoplastic polyolefin (TPO)roofing membrane exhibits a weathering color difference of from about0.25 ΔE to about 2.0 ΔE, as measured according to ASTM D2244.